diff --git a/Code/Mantid/Framework/Algorithms/src/NormaliseByDetector.cpp b/Code/Mantid/Framework/Algorithms/src/NormaliseByDetector.cpp
index 77d7563280363d0999a16c3e0a1f34d58db105c4..3273990cee9076a94a5bd768f3ddb0d2b26c2b26 100644
--- a/Code/Mantid/Framework/Algorithms/src/NormaliseByDetector.cpp
+++ b/Code/Mantid/Framework/Algorithms/src/NormaliseByDetector.cpp
@@ -176,7 +176,7 @@ namespace Mantid
       if(m_parallelExecution == true)
       {
           PARALLEL_FOR2(inWS, denominatorWS)
-          for(int wsIndex = 0; wsIndex < nHistograms; ++wsIndex)
+          for(int wsIndex = 0; wsIndex < static_cast<int>(nHistograms); ++wsIndex)
           {
             PARALLEL_START_INTERUPT_REGION
               this->processHistogram(wsIndex, denominatorWS, inWS);